Android 5.1.1 update is a bug fix release that should deal with camera crashing problems, random reboots and general stability.

To flash the OTA file you’ve downloaded, you need to sideload it with ADB from your computer by rebooting your device into RECOVERY, enabling the option to ADB SIDELOAD (apply update from adb), plugging your device to your computer and running the following command “adb sideload XXX.zip“, where XXX is the filename you’ve just downloaded.